Variable output pump

ABSTRACT

An variable output pump is disclosed. The variable output pump having a rotatable first shaft, a first pumping element mounted to the rotatable first shaft, and a coupling mechanism configured to couple the first pumping element to the first shaft for rotation therewith in a first mode, and decouple the first pumping element from the rotatable first shaft in a second mode. A method for varying the output of a fluid pump is also disclosed. The method including rotating a first pumping element and a second pumping element; and preventing rotation of the first pumping element in response to an increase in fluid pressure, while continuing to rotate the second pumping element.

TECHNICAL FIELD

The present disclosure relates generally to a pump and, moreparticularly, to a variable output pump.

BACKGROUND

Internal combustion engines, including diesel engines, gasoline engines,natural gas engines, turbine engines, and other engines known in theart, are used to drive many types of power systems. Internal combustionengines typically include an oil lubrication system and an oil pump tocirculate oil through the system. The oil pressure needed to properlylubricate an internal combustion engine may vary with the operatingconditions of the engine. As a result, pumps have been developed thatallow for the pump output to be changed or varied as desired.

U.S. Pat. No. 5,620,315 (hereinafter the '315 patent), by Pfuhler,discloses a variable output gear pump. The '315 patent discloses a pairof gears arranged axially parallel to each other. One gear is axiallyfixed while the other gear is movable in the axial direction to changethe amount of mating surface between the two gear, and thus, change theoutput from the gear pump.

While the pump disclosed in the '315 patent may provide for variableoutput, it requires a housing of sufficient size to allow one gear totranslate axially relative to another gear. Furthermore, it presentsgear loading and sealing problems due to the change in contact surfacebetween the gears and translating nature of one gear relative to theother gear.

The present disclosure is directed to overcoming one or more of theshortcomings in the existing technology.

SUMMARY

In accordance with one aspect, the present disclosure is directed to avariable output pump having a rotatable first shaft, a first pumpingelement mounted to the rotatable first shaft, and a coupling mechanismconfigured to couple the first pumping element to the first shaft forrotation therewith in a first mode, and decouple the first pumpingelement from the rotatable first shaft in a second mode.

According to another aspect, the present disclosure is directed toward amethod for varying the output of a fluid pump. The method rotating afirst pumping element and a second pumping element; and preventingrotation of the first pumping element in response to an increase influid pressure, while continuing to rotate the second pumping element.

Other features and aspects of this disclosure will be apparent from thefollowing description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which are incorporated in and constitute apart of this specification, exemplary embodiments of the disclosure areillustrated, which, together with the written description, serve toexplain the principles of the disclosed system:

FIG. 1 is a schematic illustration of an exemplary power system;

FIG. 2 is schematic illustration of an embodiment of variable outputpump for the power system of the power system of FIG. 1;

FIG. 3 is a partial cross section view of the variable output pump ofFIG. 2 in a first mode; and

FIG. 4 is a partial cross section view of the variable output pump ofFIG. 2 in a second mode.

DETAILED DESCRIPTION

Referring to FIG. 1, an exemplary power system 10 is disclosed. Thepower system 10 may include an engine 12 having a lubrication system 14.The engine 12 may include features not shown, such as fuel systems, airsystems, cooling systems, peripheries, drivetrain components,turbochargers, etc. The engine 12 may be any type of engine (internalcombustion, turbine, gas, diesel, gaseous fuel, natural gas, propane,etc.), may be of any size, with any number of cylinders, and in anyconfiguration (“V,” in-line, radial, etc.). The engine 12 may be used topower any machine or other device, including locomotive applications,on-highway trucks or vehicles, off-highway trucks or machines, earthmoving equipment, generators, aerospace applications, marineapplications, pumps, stationary equipment, or other engine poweredapplications.

The engine 12 may include an engine block 16 that at least partiallydefines a plurality of cylinders (not shown), a piston (not shown)slideably disposed within each cylinder and one or more cylinder heads18 associated with the cylinders. The engine 12 may also include acrankshaft (not shown) that is rotatable supported within the engineblock 16 by way of a plurality of journal bearings (not shown). Theengine 12 may also include one or more turbochargers 20 configured torecover energy from the exhaust of the engine 12 and use the energy tocompress air that the engine 12 will use for combustion. The one or moreturbochargers 20 may include a turbine wheel 22 and a compressor wheel24 mounted onto a rotatable shaft 26.

The lubrication system 14 transports lubricating fluid to the journalbearing, rotatable shaft 26, and other locations that requirelubrication and/or cooling. The lubrication system 14 may be configuredin a variety of ways. Any system capable of delivery lubricating fluidat appropriate pressure and temperature to critical areas in the powersystem 10 may be used.

In the depicted embodiment, the lubricating system includes a sump 32, apump 34, a pressure relief valve 36, a cooler 38, a filter 40, and afirst fluid passage 42, and a second fluid passage 44. The sump 32 maybe any suitable metallic or polymeric chamber capable of holding avolume of lubricating fluid. For example, the sump 32 may be positionedat a bottom portion of the engine 12 and function as a reservoir for thelubrication system 14.

The pump 34 is fluidly connected to the sump 32 via the first fluidpassage 42 and is configured to draw lubricating fluid from the sump 32.The pump 34 will be described in more detail below. The pressure reliefvalve 36 may be disposed in the first fluid passage 42 and configured tofluidly connect the first fluid passage 42 with the second fluid passage44 when the pressure in the first fluid passage way exceeds a pressurethreshold. Thus, the pressure of the lubricating fluid delivered to theengine 12 may be regulating by returning excess lubricating fluid backto the sump 32.

The filter 40 may be disposed in the first fluid passage 42 andconfigured to remove undesirable particles and foreign matter from thelubricating fluid. The filter 38 may be any suitable lubricating filterknown in the art. The cooler 38 may be disposed in the first fluidpassage 42 and configured to utilize a cooling medium, such as enginecoolant, to control the temperature of the lubricating fluid to adesired range prior to the fluid entering the engine 12.

The engine 12 may contain a plurality of fluid passages within theengine block 16 and cylinder head(s) 18 for routing lubricating fluid toappropriate locations within the engine 12. For example, the engine 12may include a main gallery 48 that receives lubricating fluid from thefirst fluid passage 42. From the main gallery 48, lubricating fluid maybe routed under pressure to the journal bearings (not shown), thepistons (not shown), the turbocharger shaft 26, and other enginecomponents before being returned to the sump 32.

Referring to FIGS. 2-4, the pump 34 may be configured in a variety ofways. Any pump 34 capable of selectively disengaging a pumping elementfrom a rotatable shaft may be used. In the depicted embodiment, the pump34 includes a pump housing 52 configured to form a fluid inlet 54, afluid outlet 56, and a cavity 58 connecting the fluid inlet 54 to thefluid outlet 56. Disposed within the cavity 58 are a first pumpingelement 60 mounted onto a rotatable first shaft 62 and a second pumpingelement 64 mounted onto the rotatable first shaft 62. The first shaft 62extends along a first axis 65.

The pump 34 includes a third pumping element 66 disposed within thecavity 58 and configured to be rotatably driven by the first pumpingelement 60. The third pumping element 66 may be rotatable mounted in anysuitable way. For example, the third pumping element 66 may be mountedon a rotatable second shaft 68 or a rotatable axle. A fourth pumpingelement 70 is also disposed within the cavity 58 and is mounted onto therotatable third shaft 72. The second shaft 68 and the third shaft 72 maybe coaxial along a second axis 73. The first axis 65 may be arranged inparallel to the second axis 73.

The first pumping element 60, the second pumping element 64, the thirdpumping element 66, and the fourth pumping element 70 may be configuredsubstantially similar to each other, though that is not required. In thedepicted embodiment, the pumping elements are configured as spur gears(i.e. a disc-shaped body having a straight gear face around thecircumference and a central bore for receiving a shaft). The firstpumping element 60 is configured to mate with the third pumping element66 to form a first pumping element pair 74 and the second pumpingelement 64 is configured to mate with the fourth pumping element 70 toform a second pumping element pair 76.

The second pumping element 64 and the fourth pumping element 70 may befixably mounted onto the rotatable first shaft 62 and the rotatablethird shaft 72, respectively, in any suitable manner, such as but notlimited to, fasteners, press fit, welding, pinned or keyed, or othersuitable means. The first pumping element 60 may be mounted onto thefirst shaft 62 such that in a first mode, the first pumping element 60is fixed to the first shaft 62 and rotates with the first shaft 62 andin a second mode, the first pumping element 60 is held stationary whilethe first shaft 62 rotates. A coupling mechanism 78 may be provided tocouple and decouple the first pumping element 60 and the first shaft 62.The pump housing 52 may at least partially enclose the couplingmechanism 78.

Referring to FIGS. 3 and 4, in the depicted embodiment, the firstpumping element 60 includes an inner surface 80 that defines a centralbore configured to receive the first shaft 62. The first shaft 62 may beconfigured as an elongated, generally cylindrical structure having afirst end 82 configured to extend through the bore of the first pumpingelement 60. The first shaft 62 may include an inner bore 84 extendingaxially from the first end 82 along a length of the first shaft 62. Thefirst shaft 62 may include one or more apertures 86 extending radiallyfrom the inner bore 84 through the first shaft 62.

The coupling mechanism 78 may be configured in a variety of ways. Anystructure capable of selectively coupling and decoupling the firstpumping element 60 and the first shaft 62 may be used. In the depictedembodiment, the coupling mechanism 78 includes a fluid passage 88, ainner housing surface 89 defining a cylinder 90 in fluid communicationwith the fluid passage 88, a plunger 92 disposed within the cylinder 90and configured to move axially within the cylinder, an actuator 94, adrive element 96, and a first biasing element 98.

The fluid passage 88 is configured to fluidly couple the high pressureportion of the cavity 58 (i.e. portion exposed to the outlet pressure ofthe pump 34) to the cylinder 90. A temperature actuated valve 100 may bedisposed in the fluid passage 88. The temperature actuated valve 100 maybe configured to open the fluid passage 88 when the temperature of thelubricating fluid exceeds a temperature threshold and close the fluidpassage when the temperature of the lubricating fluid is below thetemperature threshold. For example, the temperature actuated valve 100may be a wax bulb type thermostat that moves a valve element (not shown)at a preset temperature to open the fluid passage 88 and at anotherpreset temperature to close the fluid passage 88.

The plunger 92 may be a substantially cylindrical structure having anend portion 102 that forms an end face 104 and a cylindrical skirt 106extending axially from the end portion 102. The skirt 106 forms a recessconfigured to receive the first end 82 of the first shaft 62. Positionedat the distal end of the skirt 106 is an interface 108 configured toengage the first pumping element 60 and prevent the first pumpingelement 60 from rotating when the first pumping element 60 is decoupledfrom the first shaft 62. The interface may be configured in a variety ofways. For example, the interface 108 may be an edge or projectionconfigured to engage an interface surface 110 or recess in the firstpumping element 60.

The actuator 94 may be configured to move axially in the cylinder 90 inresponse to movement of the plunger 92. The actuator 94 may be generallycylindrical projection extending along the first axis 65 and include afirst end 112 configured to engage the end portion 102 of the plunger 92and a second end 114 configured to be received within the inner bore 84the first shaft 62. The actuator 94 may have an intermediate portion 116having a diameter less than the diameter of the second end 114 connectedto the second end 114 by a tapered portion 118. The first end 112 may bedisposed radially inward from the skirt 106 and may loosely engage, befixably attached to, or be integrally formed with the end portion 102 ofthe plunger 92.

The drive element 96 may include one or more engagement portions 120 anda second biasing element 122. The drive element 96 may be configured tomove between a first position in which the engagement portions 120 areradially expanded to engage the inner surface 80 of the first pumpingelement 60 and a second position in which the engagement portions 120are radially retracted away from the inner surface 80. The secondbiasing element 122 may be connected to the engagement portions 120 tobias the engagement portions 120 away from the inner surface 80.

The first biasing element 98 may be positioned within the inner bore 84of the first shaft 62 between an inner radially extending surface 124 ofthe first shaft 62 and the second end 114 of the actuator 94. The firstbiasing element 98 being configured to bias the actuator 94 axially awayfrom the first shaft 62.

One or more sealing elements 126 may be configured to provide a fluidseal between the plunger 92 and the inner housing surface 89. Forexample, an annular seal 126 may be received in a groove (not shown) inthe inner housing surface 89 to provide a seal against lubricating fluidthat enters the cylinder 90 from flowing past the plunger 92 toward thefirst pumping element 60.

INDUSTRIAL APPLICABILITY

The disclosed pump 34 may be applicable to any application in which itwould be beneficial to have more variable output from the pump. Forexample, the disclosed pump 34 may be used as a lubricating fluid pumpfor a power system, such an engine and thus provide sufficientlubricating fluid pressure at idle conditions without wasting energywith excessive capacity at higher engine speeds. The operation ofexemplary power system 10 will now be explained.

During engine operation, to prevent damage to engine components frommetal-to-metal contact, the lubrication system 14 is configured totransport lubricating fluid to the journal bearing, turbocharger shaft26, and other locations in the engine that require lubrication and/orcooling. In operation, the pump 34 draws lubricating fluid from the sump32 and through the lubrication system and engine 12 as described abovein relation to FIG. 1.

The pump 34 is driven via the third shaft 72 by the engine 12, forexample. Since the fourth pumping element 70 is fixably mounted to thethird shaft 72, rotation of the third shaft 72 rotates the fourthpumping element 70. The second pumping element 64 mates with the fourthpumping element 70. Thus, rotation of the fourth pumping element 70rotates the second pumping element 64. Since the second drive element 64is fixably attached to the first shaft 62, rotation of the secondpumping element 64 rotates the first shaft 62.

In a first mode, the first pumping element 60 is fixed for rotation withthe first shaft 62. In particular, as shown in FIG. 3, the temperatureactuated valve 100 is in closed and blocking the fluid passage 88. Thisoccurs when the temperature of the lubricating fluid in the pump 34 isbelow the temperature threshold. When the fluid passage 88 is blocked,the plunger 92 is not exposed to fluid pressure from the lubricatingfluid, thus the first biasing element 98 will bias the plunger 92 to afirst position in the cylinder 90 (to the far right as illustrated inFIG. 3).

When the plunger 92 is in the first position, the second end 114 of theplunger 92 is radially inward of the drive element 96. Thus, theengagement portions 120 are radially extended against the bias of thesecond biasing element 122 to engage the inner surface 80 of the firstpumping element 60. As a result, the first pumping element 60 is fixedrelative to the first shaft 62 for rotation therewith.

The third pumping element 66 mates with the first pumping element 60 andis rotatably mounted. Thus, rotation of the first pumping elementrotates the third pumping element 66. In the first mode, both the firstpumping element pair 74 and the second pumping element pair 76 areactive.

If the temperature of the lubricating fluid exceeds the temperaturethreshold and the lubricating fluid exceeds a pressure threshold, thepump will be placed in a second mode. In the second mode, the firstpumping element 60 is decoupled from the first shaft 62, thusdeactivating the first pumping element pair 74.

In particular, as shown in FIG. 3, when the lubricating fluidtemperature exceeds the temperature threshold, the temperature actuatedvalve 100 will open and lubricating fluid under pressure will flowthrough the fluid passage 88 and impinge upon the end face 104 of theplunger 92. If the fluid pressure exceeds the pressure threshold (i.e.sufficient tot overcome the bias of the first biasing element 98), theplunger 92 will move from the first position to a second position (asshown in FIG. 4).

When the plunger 92 is in the second position, the intermediate portion116 of the plunger 92 is radially inward of the drive element 96. Sincethe diameter of the intermediate portion 116 is smaller than thediameter of the second end 114, the second biasing element 122 may biasthe engagement portions 120 are radially inward, thus; disengaging theengagement portions 120 with the inner surface 80 of the first pumpingelement 60.

In addition, when the plunger 92 is in the second position, theinterface 108 engages the interface surface 110 of the first pumpingelement 60 to prevent the first pumping element 60 from rotating orspinning freely. Thus, in the second mode, the first pumping elementpair 74 is deactivated while the second pumping element pair 76 remainsactive.

The disclosed pump, therefore, may provide full pumping capacity whenthe temperature and the pressure of the lubricating fluid are belowpredetermined thresholds, such as when the engine is operating a lowidle. When the temperature and the pressure exceed predeterminedthreshold, the capacity of the pump may be reduced since at higherspeeds the lubricating fluid quantity required to maintain sufficientpressure is significantly less than the full pump capacity. As a result,wasted energy in the form of pressurized lubricating fluid returned tothe sump 32 can be reduced.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed dosing system.Other embodiments will be apparent to those skilled in the art fromconsideration of the specification and practice of the disclosed methodand apparatus. It is intended that the specification and examples beconsidered as exemplary only, with a true scope being indicated by thefollowing claims and their equivalents.

1. A variable output pump, comprising: a rotatable first shaft; a firstpumping element mounted to the rotatable first shaft; and a couplingmechanism configured to couple the first pumping element to the firstshaft for rotation therewith in a first mode, and decouple the firstpumping element from the rotatable first shaft in a second mode.
 2. Thevariable output pump of claim 1 wherein the coupling mechanism switchesbetween the first mode and the second mode in response to a change influid pressure.
 3. The variable output pump of claim 2 wherein thecoupling mechanism switches between the first mode and the second modein response to a change in fluid temperature.
 4. The variable outputpump of claim 1 further comprising a second pumping element mounted tothe rotatable first shaft, wherein the second pumping element remainscoupled to the first shaft in the second mode.
 5. The variable outputpump of claim 1 wherein the first pumping element is a first gear andthe second pumping element is a second gear, and the pump furthercomprises a third gear configured to mate with the first gear and afourth gear configured to mate with the second gear
 6. The variableoutput pump of claim 5 wherein the third gear is mounted on a secondrotatable shaft and the fourth gear is mounted on a third rotatableshaft.
 7. The variable output pump of claim 1 comprising a plungerconfigured to translate axially between a first position and a secondposition to switch the variable output pump from the first mode to thesecond mode.
 8. The variable output pump of claim 8 further comprising abiasing element configured to bias the plunger toward the firstposition.
 9. The variable output pump of claim 8 wherein the plungerincludes an interface configured to prevent the first pumping elementfrom rotating when the plunger is in the second position.
 10. Thevariable output pump of claim 1 further comprising a drive elementconfigured to move radially inward to decouple the first pumping elementfrom the rotatable first shaft.
 11. A method for varying the output of afluid pump, comprising: rotating a first pumping element and a secondpumping element; and preventing rotation of the first pumping element inresponse to an increase in fluid pressure, while continuing to rotatethe second pumping element.
 12. The method of claim 11 wherein the stepof rotating a first pumping element and a second pumping element furthercomprising rotating a first shaft.
 13. The method of claim 12 comprisingdecoupling the first pumping element from the first shaft.
 14. Themethod of claim 13 comprising opening a fluid passage in response to afluid temperature exceeding a temperature threshold.
 15. A power system,comprising: an engine; a sump configured to hold a volume of fluid; anda variable output pump configured to draw fluid from the sump anddeliver the fluid to the engine, the variable output pump, comprising: arotatable first shaft; a first pumping element mounted to the rotatablefirst shaft; and a coupling mechanism configured to couple the firstpumping element to the first shaft for rotation therewith in a firstmode, and decouple the first pumping element from the rotatable firstshaft in a second mode.
 16. The power system of claim 15 wherein thecoupling mechanism switches between the first mode and the second modein response to a change in a pressure of the fluid.
 17. The power systemof claim 16 wherein the coupling mechanism switches between the firstmode and the second mode in response to a change in fluid temperature.18. The power system of claim 15 further comprising a second pumpingelement mounted to the rotatable first shaft, wherein the second pumpingelement remains coupled to the first shaft in the second mode.
 19. Thepower system of claim 17 wherein the first pumping element is a firstgear and the second pumping element is a second gear, and the pumpfurther comprises a third gear configured to mate with the first gearand a fourth gear configured to mate with the second gear.
 20. Thevariable output pump of claim 15 comprising an interface configured toprevent the first pumping element from rotating when the couplingmechanism is in the second mode.